Fuse



Patented Dec. 16, 1924.

UNITED STATES ARCHIBALD GRIEVE, GF ESTEORT,

GONNECTCUT,

FUSE.

Application filed February 4, 1921.

To all tri/1,0m t may concern.'

Be it known that I, ARCHIBALD Gnmvn, a subject of the King of Great Britain, residing at Viestport, in the county of Fairfield and State of Connecticut, have invented certain new and useful Improvements in Fuses, of which the following is a specification.

My invention relates to fuses, and particularly to reiillable cartridge fuses of the blade type. Among the objects of my invention may be particularly mentioned-nist, the provision of an end construction for the fuse such that the detachable parts may be removed and securely replaced without the use of tools of any description, while at the saine time insuring an excellent contact between the terminal element and the fuse strip; second, the provision of a removable element at the end of the fuse casing, which, while comprising a group of independent elements, may be readily handled as a unit and thus minimize the danger of loss of parts and delay in handling during the renewal of the fuse strip; third, the reduction of the number of removable end parts to the least. possible number consistent with etticient protection; fourth, the exterior display of a rated end of the fuse strip, while at the same time preventing the dangerous escape of hot gases through the passage in which said end of the fuse strip lies; fifth, the prevention of gas escape through the threaded connection between the screw ferrule and end bushing; sixth, the provision of a gas expansion chamber between the fuse chamber and gas vents to prevent the escape of molten metal or iiame through the latter, and in this connection particularly a construction which permits the expansion chamber to vary with fuses of different capacities within the range of the fuse structure, without, however, lessening the security against gas escape; seventh, the provision of an extended gas escape passage between the expansion chamber and veut, by means of which the gases are compelled to change their direction of travel several times and to pass in contact with extended cooling surfaces before they emerge through the vent or vents; eighth, a construction of the parts such that the insertion of a fuse strip of a capacity greater than that for which the fuse is designed is rendered impossible; ninth, the secure anchorage of an end bushing to the cartridge casing in a manner Serial No. 442,515.

which prevents the entry of between the bushing neck and casing wall to the injury of the latter; tenth, the provision of various features of improved construction hereinafter pointed out or shown in the acconipanying drawings, in which- Fig. l is a broken longitudinal side elevation of a fuse in which my invention is embodied in one form;

Fig. 2 through Fig. 3 is a perspective of the casing element with end caps and associated parts removed, and showing a fuse strip partially inserted;

Fig. #i is a longitudinal section on the line i-Ll, 2, drawn to a larger scale;

Fig. 5 is a section on the line '5e-5, ifig. Li; and

lfig. 6 is a perspective of a gas-deiiccting washer.

To illustrate the invention, which is susceptible of embodiment in various modified constructions, l have shown a fuse comprising a tubular casing i' of fiber, or other suitable insulating material, having permanently secured in the opposite ends thereof metallic bushings 8 and 9. Each bushing is provided with a necll: l() which is forced into the end of the iiber casing T and riveted in position at il. The exterior face of the neck is preferably serrated as shown, in order to not only grip the material of the casing, but also to prevent the escape of gas between the casing and the bushingnecl; on the blowing of the fuse. rihe end of each bushing has an integral end closure diaphragm 'l2 provided with an opening i3, through which the end of the fuse strip iimay be passed. il stud l5 seured to the diaphragm l2 forms the pivot on which a shutter 1G is mounted. 'lhis shutter normally clo the opening l?) in the diaphragm save for the narrow passageway afforded for the exit of the fuse strip therethrough from the fuse chamber. Si second stud 25 carried by the diaplirgain i2 on the opposite side of the opening lf3. forms a stop which limits the movement of the shutter in one direction. The ends l? and 1S of the strip emerging from the opposite ends ofthe fuse chamber are angled over the shutters i6, the end i8 having a terminal extension i9. This extension 'i9 is bent baci; into a shallouY groove Q0 formed in the exterior of the bushing and adjacent poris a longitudinal section therelll) tion of the casing 7, and is of such length that its free end, which bears an indication of its rating, lies exposed beyond the margin of the end ferrule 2l.

The removable end members of the fuse comprise in addition to the screw ferrule 2l, the terminal blades 22, by which the fuse is electrically connected to the clips of the fuse holder in adjusted position. These blades are provided with circular base flanges or discs 23, which rest directly upon the bent-over ends 17 and 1.8 of the fuse strip and make contact therewith. In order to secure the alinement of the blades at opposite ends of the fuse, holes 24 are punched in the base flanges 23 and register with the projecting heads of the studs l5 and 25 on the bushings S and 9. The base flange of each blade 22 is thus spaced from the shutter i6 and from the end of the bushing, thus affording an expansion chamber 26, into which the gases from the fuse chamber enter on the blowing of the fuse. In order to permit the escape of the gases from the eXpansion chamber, the holes 24 in the base fianges 23 are of greater diameter than the heads of the studs l5 and 25, and the latter may be of cone shape, as indicated, to afford sufficient passageway for this purpose. Inasniuch as the direct escape of the hot gases. even as cooled in the expansion chamber, 'would be dangerous, I provide a gas del'lecting and cooling washer 27 slightly spaced by dimunitive studs 28 from the cuter face of the base fiange 223, and provided with a central slot 29, which permits the washer to be passed over the blade 22, but closely engaging the latter to prevent the escape of gases at this point. The washer is pierced by perforations 30 of any suitable size and number to permit the gases to pass therethrough. It will be obvious that the gases are thus forced to spread out between the top of the base flange 23 of the blade 22 and the inner face of the washer 27 in order to pass to the outer face of the latter through the holes 30.

Further restricting the passage of the gases is ya relatively light metal thimble 3l, the marginal flange of which closely embraces the washer 27, the base (lange 23 of the blade 22, the shutter 16, and the reduced end 32 of the bushing 9. This snug fit of the thimble flange upon the reduced end 32 ol' the bushing not only confines the gases to the expansion chamber 26, thus forcing them to pass out through the perfor-ations 3l). but it also prevents the escape of the gases to the threaded area oit' the bushing and ferrule-a feature of first importance in a renewable fuse, since the entry of the hot gases between the ferrule threads is ver'v apt to cause the latter' to bind so hard that the lmscrewing of the ferrule becomes a practical impossibility. The thimhle Si effectually prevents this. The gases passing through the holes il() `in the washer, and coming into contact with the inner face ot' the thimble end, are again deflected by the latter and are forced to flow toward the blade 22, where they escape through the slot 33 in the thimble end at a temperature and pressure so reduced as to prevent injury to adjacent objects. The notch 3l (Fig. l) in the marginal flange of the thimble through which the rated end lt) of the fuse strip passes to the channel 20, so closely fits the strip that when the parts are assembled practically no gas escapes at this point.

To hold the detachable cnd elements of the fuse assembled, l provide the ferrules 2l with interiorly threaded skirts, which engage the externally threaded area of the bushing, while the inwardly turned flange 36 bears upon the marginal area of the end face ol` the thimble 3l. ltis obvious that on screwing up the ferrule its flange 2;6 exerting pressure through the thimble 3l and washer 2i', forces the base 'flange 23 of the blade terminal 22 firmly down upon the bent-over end of the fuse strip and establishes a good electrical contact between these parts without any tendency to injun` the fuse strip. At the same time the screw ring holds the thiinble 3l in such close engagement with the reduced end 32 of the bushing that the lateral escape of the gases to the threaded a rea is sul'istantially prevented, and no appreciable gas escape occurs in this direction as above stated. T he central opening of the ring leaves the cern tral area of the thimble 231Y unsupported` so that when the gases under pressure escape through the holes 23() in the washer 27 to the space between the latter and the thimble, the latter is slightly distorted outward and permits thc flow of gases to the vent passage -l 'lhis flexion of the thimble serves the purpose of a reducing valve, which further limits the pressure of the gases coming from the expansion chaniber and now substantially cooled by their Contact with the extended metal surfaces in contact with which they have been forced to travel'.

It is obvious that the circutous path which the gases are thus forced to travel in contact with heat absorbing and radiating metallic surfaces, extracts from the gases substantially all their dangerous heat, so that upon their exit they are at a temperature below that at which they are likely to ignite any inflammable material in their immediate neighborhood, or to injure adjacent equipment. Moreover, the expansion intermediate the fuse chamber and the vent, and the reducing valve a'ect secured by the distortion of the end of the thimble 31, practically eliminate the dangerous pressure at which the gases would otherwise escape. The shallow groove 2O in which the exposed llbb lli

end 19 of the fuse strip lies, is substantially filled by the latter, while the pressure of the thiinble 81 and the ferrule 2l against the end of the .fuse strip substantially seals the groove 2O against the escape of gases at this point. Moreover, it will be noted that the groove 2O is situated at the side of the expansion chamber opposite that which the gases enter the latter through the opening from the fuse chamber, consequently they readily pass out through the holes 24 before reaching the groove.

rlhel diameter of the skirt of the thimble so predetermined with relation to the diameter of the reduced end of the thinible that when the thiinble is in position on the latter its skirt hugs the reduced area 32 so closely that the escape of gas at this point is substantially, if not absolutely, prevented.

s Again, the zigzag path which the gases must travel to escape at the edge of the slrirt of the thiinble impedes their travel and further tends to prevent their passage in this direction. lt may be pointed out that the reduced end 32 of the bushing is cylindrical, and the skirt of the thimbie similarly shaped so that the latter may accommodate itself to the various positions assumed by it as a result of dierent thicknesses of the fuse strip for fuses of different capacity, within the range of the fuse cartridge, without the loss of the security against gas escape at this point.

Mechanically, the operation of renewal is simple. Upon unscrewing the ferrule 2l the blade 22 carrying the thimble 31 and washer 27 is removed with the ferrule, and these parts form a unit and remain assen'ibled. Even should the ferrule become detached from the blade, the parts associated with the latter, viz, the thimble 81 and washer 2"?, remain assembled on the blade by reason of the frictional engagement between these parts. After the ferrule, blade, and associated parts have been removed, the shutter 16 is readily swung open to expose the opening 13 through which the blown fuse parts may be removed and a new fuse strip inserted. To re-assemble the parts it is only necessary to insert the new fuse strip, close the shutters, angle over the fuse ends, position the blades on the studs, and screw up the lcrrules, thus mechanically and electrically connecting the parts again for re-use. ln order to facilitate the manipulation of the ferrules, they may be externally lrnurled, as shown in Fig. l. It is obvious that the present construction has the marked advantage over all the renewable fuses now on the market, that to effect the renewal operation no tools whatever are required, since the nnscrewing and screwing up of the ferrules is accomplished solely by hand. rlie fuse strip requires no connection by binding or clamping screw to the blade element, while l claimp i. L cartridge fuse having an end conyon coinprisii'g a blade contact with adapted to rest upon and make ith the end of a fuse strip, a thiinble Iittii'ig over the blade and havingv marginal fia ge embracii ,j the blade base, 2 Ad a gas-deflccting wasner interposed .between said base and the end of the thimble.

2. fr cartridge fuse having an end construetfon con'iprising a. blade contact with base flange adapted to rest upon and inalie contact lwith the end of a fuse strip. a thiinble litting over the. blade and having a marginal flange einbracing-l Ahe blade base. ad a gas-deflecting washer interposed bee oase and the end of the thiinble. gether with a draw-up ring embracing the l1y and serving to effect the assembly Y parts at the end of the tusc.

i cartridge fuse havingl an end construction comprising a blade contact with base flange adapted to rest upon and make t :t with the end of a fuse strip, a thi .ihre fitting over the blade and having a u'nirginal flange embracing the blade lmsc. and a gas-deliecting washer interposed bc- 1[Tween said base and the end of the thiinble` together with means associated with said base flange to hold the blade in prede"erni'ned relative rotary position with respect to the fuse casing.

4l. ln a cartridge fuse, a substantially closed fuse chamber having` an exit for the fuse strip, a blade terminal having a base flange adapted to bear against an offset end of the fuse a thimble encasing said blade base and the. end of the fuse chamber, und a ferrule enclosin` the thiinblc and base of the blade termina and serving to hold the parts assembled at the end of the fuse chamber, together with a gas-dcllecting washer arranged between the base 'flange of the blade and the end of the thi'inble.

5, ln a ca fuse, a substantiall \,v closed fuse chamber haring an exit for the fuse strip, a blade terminal having a base lia e adapted to bear against an oi'lsct end of the fuse strip, a thinible encasing said blade base and the end of the fuse chamber. and Tier-rule. snrrouinling the thimble and baz-,1e of the blade terminal and serving to hold the parts assembled at the end of the fuse chamber, together with positioning stud means at the end of the fuse chamber, and cooperatingV engaging means on the base flange oi the fuse blade.

G. ln a cartridge fuse, a substantially closed fuse chamber haring an exit for the fuse strip, a blade terminal having' a base `liange adapted to bear against an otl'set end ot the Afuse strip, a thimble encasing said blade base and the end et the tnse chamber, and a ferrule surrounding the tliimble and base ot the blade terminal and serving to hold the parts assembled at the end of the tuse chamber, together with positioning stud means at the end of the 'tuse eliamber, the base iiangre ot' the tuse blade having recesses looselyv engaging said stud means to position the blade and to afford venting apertures Jtor the lases generated in the fuse chamber on the blowing ot the fuse.

't'. ln a cartridge t'use.` a fuse casing and end bushing 'tast thereon and havint;A an end opening` t'or the exit ol' the 'tnse strip, a fuse terminal adapted to treel)Y bear on the bentover end of said fuse strip supported on said bushine" O'as def-lectingl means. and an end cap or thimbleassociated therewith and forming a removable unit, together with a lierrule for holding:r said terminal unit as sembled. with the bushing.

In a cartridge fuse, a tubular casing forming a fuse chamber 'with fuse exits at opposite ends thereofA` means t'ormintr an eX- pansion chamber at. one end oi the easing, a distortable light metal member impeding the escape ot' lfases t'rom said expansion chan'iberI` and a screw ferrule, for holding said impedingl member in obstructing position.

9. ln a cartridge fuse, the combination of a 'fuse casing, a bushing,r secured in the end thereof` said bushing' having; a reduced end, in combination `with a removable tliimble or cap smflgly fittingr said reduced end oit' the bushing and serving' to obstruct the escape of gases from the fuse chamber. in combination with means for holding said thimble in obstructing!` position. said thin'ihle being distortable to permit the escape ot' rases through a rent in the end thereof.

In testimoniv whereof l have signed my name to this specification.

RCHTBA LD GRI EVE. 

